Preheat oven to 400°. Scrub potatoes (no need to peel) and cut into 1-inch cubes.

Combine salt, granulated garlic, and black pepper in a medium bowl. Add chicken and turn to coat.

Set a 12-inch cast-iron skillet over medium-high heat and add grapeseed oil; heat until oil starts to shimmer and smoke a little, 2 to 5 minutes.

Add chicken to hot oil, skin-side down. Sear chicken until the skin is golden brown, about 5 minutes. (If seasonings start to get dark, reduce heat a bit.) Flip and continue cooking until chicken is browned on the second side, a few minutes longer. Using tongs, transfer chicken from skillet to a sheet pan or plate and set aside.

Add cubed potatoes to skillet and cook, stirring occasionally, until light golden brown, 10-12 minutes. Transfer to the medium bowl. Add carrots to skillet and cook until they begin to caramelize in spots, stirring frequently, about 5 minutes.

Stir minced garlic and oregano into carrots and remove skillet from heat. Stir in potatoes. Return chicken to skillet, placing it on top of vegetables, skin-side up, and pouring any juices into the pan.

Place skillet in preheated oven and roast until the temperature of the chicken in the thickest part reaches at least 165° on a thermometer and vegetables are tender when pierced, 15-20 minutes. Carefully remove skillet from oven. Scatter parsley over chicken and serve.